At least 257 people were killed when an Algerian military plane crashed outside the capital, Algiers, the country’s defense ministry said, the world’s deadliest aviation disaster in almost four years and the nation’s worst ever.

The plane went down in a field at 7:50 a.m. local time Wednesday, shortly after departing Boufarik military air base southwest of the capital, the ministry said. It was bound for Bechar, Algeria, near the Moroccan border, with a stop in Tindouf, the military said.